chromium/android_webview/tools/system_webview_shell/test/data/experimental/basic-logging.html

<!DOCTYPE html>
<html>
  <script src="../resources/js-test.js"></script>
  <body>
      SOMETEXT
    <script type="text/javascript">
      description("Test JavaScript feedback into WebView");
      debug("some debug text");
      debug(isWorker());
      debug(window.testRunner);
    </script>
  </body>
</html>